The output of the oscillator in the embodiment of the invention to be described has a low distortion sinusoidal waveform, and the frequency of the output is controlled by a direct-current input signal. The oscillator is capable of generating two output signals displaced 90.degree. in phase from one another. The ability of the oscillator to produce two-phase quadrature output signals makes it useful for polyphase applications, as mentioned above. For example, by combining the two output signals, an output signal of any desired phase displacement may be synthesized.
The oscillator of the invention is particularly, though not exclusively, useful for supplying reference signals to multiphase alternating-current induction motor speed controls. Its other applications include, for example, telemetry systems, frequency synthesizers, phase-lock loop communication detector circuits, and the like.